1. Field of the Invention
The present invention relates to a charge-imparting member which is used for imparting an electric charge uniformly to an object such as a photoreceptor of an image-forming apparatus such as an electrophotographic copying machine or printer, or a toner-jet copying machine or printer.
2. Background Art
In image-forming apparatuses such as electrophotographic copying machines and printers and toner-jet copying machines and printers, members such as a charge-imparting roll, a development roll, a toner controller, an intermediate transfer roll, and a belt must be endowed with properties such as a non-staining property to a photoreceptor or a similar member, and conductivity and friction coefficient of certain levels. Accordingly, such members formed of a material such as polyurethane or silicone rubber have conventionally been used. However, such polymer-made members are replaced with those provided on an elastic layer in combination with a coating layer or a coating tube, in view of an anti-staining property to a photoreceptor or a similar member; chargeability; and for other reasons.
Specifically, Japanese Patent Application Laid-Open (kokai) No. 5-204234 discloses a development roller provided on a conductive sponge layer having a conductive outermost layer formed of a polyamide resin tube. Japanese Patent Application Laid-Open (kokai) No. 7-134467 discloses a charge-imparting member having a surface layer containing a lubricant such as wax. Japanese Patent Application Laid-Open (kokai) No. 8-160701 discloses a charge-imparting member having a coating layer formed of a fluorocarbon-containing conductive polymer or having a surface layer formed of a seamless tube.
However, a surface layer provided through a method such as a direct application method does not necessarily attain satisfactory adhesion to a substrate and so may have poor durability. Thus, such a surface layer disadvantageously poses a problem of poor long-term reliability. Similarly, a surface layer formed of a seamless tube exhibits lower processability and is produced at high cost. In addition, since the surface layer is isolated with an elastic layer, problems such as insufficient charging characteristics arise.
In order to solve the above-described problems, the present inventors previously developed a development roller provided with a surface-treated layer which had been produced by treating the surface of the roller with an isocyanate compound (Japanese Patent Application Laid-Open (kokai) No. 5-173409), in an attempt to produce a charge-imparting member which can be formed easily and exhibits excellent durability by virtue of a monolithic structure with an elastic layer. However, the development roll provided with an isocyanate-treated layer requires high rotation torque and possibly poses drawbacks such as jitter, filming, and toner conveyance.
In view of the foregoing, the present inventors have carried out extensive studies so as to solve the aforementioned problems. Thus, an object of the present invention is to provide a charge-imparting member which can be produced at low cost and can maintain favorable characteristics for a long period of time.
Accordingly, in one aspect of the invention, there is provided a charge-imparting member comprising an elastic layer formed of an epichlorohydrin rubber material and a surface-treated layer formed by use of a surface treatment liquid containing at least one polymer selected from among an acrylic fluoropolymer and an acrylic silicone polymer; a conductivity-imparting agent; and an isocyanate component.
The elastic layer may be formed of a material containing at least one species selected from the group consisting of epichlorohydrin rubber, an epichlorohydrin-ethylene oxide copolymer, and an epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer.
The elastic layer may have a rubber hardness of 30xc2x0 to 70xc2x0 as specified in JIS A.
The conductivity-imparting agent may comprise at least one electron-conductive conductivity-imparting agent selected from the group consisting of a metal oxide micropowder and carbon black.
The conductivity-imparting agent may comprise an ion-conductive conductivity-imparting agent and at least one electron-conductive conductivity-imparting agent selected from the group consisting of a metal oxide micropowder and carbon black.
The surface treatment liquid may contain the conductivity-imparting agent in an amount of 10-40 wt. % based on the isocyanate component.
The surface treatment liquid may contain at least one polymer in a total amount of 2-30 wt. % based on the isocyanate component.
The surface-treated layer may be formed by impregnating the surface of the epichlorohydrin rubber material with the surface treatment liquid and heating.
According to the present invention, the surface-treated layer is monolithically provided in the surface of the charge-imparting member, and uniformly contains carbon black and the acrylic fluoropolymer or the acrylic silicone polymer. Since the thus-formed surface-treated layer is prepared by impregnating the surface of the rubber member with a surface treatment liquid, the density of the formed surface layer gradually decreases from the surface to the inside. Thus, the present invention can provide a charge-imparting member which is not contaminated during contact with an organic photoreceptor, exhibits small environment-dependent variance in electrical characteristics, and has an excellent anti-toner-filming property.